Detect audio output + suggestion for a speech synthesis library

Question

I would like to detect if my PC is playing any kind of audio (music/movie anything).
I wrote an app which notifies me of my twitter updates. Now I would like to add a speech synthesis to it but I only want to play out the messages if there is no music or movie playing.

Although I'm using C# I don't mind doing the detection using C++ and then integrating it.

So the questions are:

1) How can I detect audio output?
2) What is the best free speech synthesis library for windows?

Answer 1

After some time looking through the MSDN I have found the solution.

Using the loopback recording you can listen to what's being outputted to the audio output device.

http://msdn.microsoft.com/en-gb/library/windows/desktop/dd316551(v=vs.85).aspx

This link also refers to an example of how to capture the stream:

http://msdn.microsoft.com/en-gb/library/windows/desktop/dd370800(v=vs.85).aspx

In here you can get the buffer data as shown in the example by calling:

pCaptureClient->GetBuffer(...)

All you have to do then is to check the value of those bytes. If they are all 0s then there is nothing playin..

For the speech synthesis I used the SpeechSynthesizer .NET class

http://msdn.microsoft.com/en-us/library/system.speech.synthesis.speechsynthesizer.aspx